Brunswick
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Brunswick clear sky chart from 2005-11-06 to 2024-11-05.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	10% 6% 2 6% 5% 5% 5% 5% 7% 9% 41%	101034
	Night	10% 6% 2 6% 5% 4 5% 4 6% 9% 41%	97957
Transparency	Day	34% 10% 17% 20% 14% 5%	104776
	Night	37% 9% 14% 18% 16% 7%	102354
Seeing	Day	10% 6% 20% 30% 24% 10%	15434
	Night	12% 6% 20% 32% 26% 5%	25488

By Month

Percentage Cloud Cover SE (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	11% 8% 2 5% 5% 5% 4 3 5% 7% 46%	2836
	11th to 20th	Day	12% 7% 2 7% 5% 4 4 3 5% 7% 44%	2840
	21st to end	Day	12% 7% 3 7% 4 4 4 3 5% 7% 44%	3124
February	1st to 10th	Day	15% 8% 2 5% 4 4 4 4 5% 6% 42%	1852
	11th to 20th	Day	13% 6% 2 5% 4 4 4 4 5% 6% 48%	1848
	21st to end	Day	13% 6% 2 5% 3 3 3 3 4 8% 48%	1641
March	1st to 10th	Day	15% 9% 3 7% 4 4 4 3 5% 7% 37%	3435
	11th to 20th	Day	7% 4 1 4 4 4 4 4 6% 9% 53%	3480
	21st to end	Day	16% 7% 2 6% 4 4 4 3 5% 7% 43%	3815
April	1st to 10th	Day	8% 5% 2 5% 4 4 3 3 6% 8% 51%	2090
	11th to 20th	Day	10% 5% 3 6% 5% 3 4 4 5% 7% 48%	2157
	21st to end	Day	6% 3 2 4 4 4 4 4 5% 8% 57%	2332
May	1st to 10th	Day	6% 3 1 4 4 4 4 4 6% 11% 53%	4082
	11th to 20th	Day	10% 7% 3 6% 5% 5% 5% 4 6% 9% 41%	4081
	21st to end	Day	6% 3 1 4 4 5% 5% 5% 7% 10% 50%	4476
June	1st to 10th	Day	9% 6% 2 6% 5% 6% 7% 5% 10% 11% 33%	2470
	11th to 20th	Day	5% 5% 1 7% 6% 6% 7% 5% 9% 12% 37%	2470
	21st to end	Day	8% 5% 2 8% 6% 7% 8% 8% 9% 12% 28%	2470
July	1st to 10th	Day	7% 6% 2 8% 6% 8% 8% 8% 9% 11% 26%	4120
	11th to 20th	Day	4 3 2 5% 6% 6% 8% 7% 11% 15% 32%	4120
	21st to end	Day	4 4 2 6% 7% 8% 8% 8% 10% 14% 29%	4466
August	1st to 10th	Day	13% 6% 3 8% 6% 7% 7% 5% 8% 11% 26%	4104
	11th to 20th	Day	5% 4 2 6% 5% 6% 6% 6% 9% 12% 39%	4026
	21st to end	Day	9% 5% 3 8% 5% 6% 6% 6% 8% 10% 33%	3930
September	1st to 10th	Day	12% 7% 2 8% 6% 7% 7% 5% 7% 9% 29%	2090
	11th to 20th	Day	14% 7% 3 9% 6% 6% 7% 5% 6% 8% 29%	2090
	21st to end	Day	13% 7% 3 7% 5% 5% 4 4 6% 9% 37%	2090
October	1st to 10th	Day	12% 7% 2 7% 5% 4 6% 3 5% 8% 41%	2033
	11th to 20th	Day	7% 4 2 4 3 4 4 3 6% 7% 55%	1900
	21st to end	Day	10% 5% 2 5% 4 3 4 3 5% 8% 52%	2090
November	1st to 10th	Day	11% 5% 2 5% 4 4 4 3 5% 7% 51%	1898
	11th to 20th	Day	11% 7% 2 5% 4 4 3 3 4 7% 49%	1881
	21st to end	Day	12% 7% 2 5% 4 3 4 4 6% 8% 45%	1710
December	1st to 10th	Day	11% 6% 2 6% 5% 4 4 3 5% 8% 46%	1710
	11th to 20th	Day	16% 6% 2 6% 4 3 3 3 5% 7% 45%	2153
	21st to end	Day	15% 8% 3 6% 5% 4 4 3 4 5% 43%	3124
January	1st to 10th	Night	14% 7% 3 7% 5% 3 4 3 6% 7% 42%	4109
	11th to 20th	Night	8% 8% 4 7% 4 4 5% 4 6% 8% 42%	4120
	21st to end	Night	12% 8% 3 8% 4 4 3 3 5% 7% 41%	4532
February	1st to 10th	Night	16% 7% 3 7% 3 4 4 3 5% 6% 42%	2323
	11th to 20th	Night	14% 8% 2 7% 4 4 3 3 5% 5% 46%	2218
	21st to end	Night	13% 6% 2 5% 4 4 5% 4 6% 6% 45%	1810
March	1st to 10th	Night	18% 12% 4 6% 4 3 3 3 4 5% 37%	3418
	11th to 20th	Night	8% 5% 2 4 3 4 4 3 6% 10% 52%	3480
	21st to end	Night	13% 6% 3 6% 4 4 4 3 5% 7% 46%	3817
April	1st to 10th	Night	9% 5% 1 5% 4 4 5% 4 6% 8% 49%	2090
	11th to 20th	Night	9% 6% 2 5% 5% 3 5% 3 5% 7% 51%	1970
	21st to end	Night	5% 3 1 4 4 4 4 3 7% 9% 56%	1862
May	1st to 10th	Night	5% 4 1 5% 4 5% 5% 5% 7% 9% 52%	2813
	11th to 20th	Night	11% 6% 2 6% 5% 4 5% 4 6% 9% 44%	2812
	21st to end	Night	6% 4 2 4 5% 3 5% 4 7% 10% 51%	3079
June	1st to 10th	Night	9% 5% 2 6% 5% 7% 6% 5% 8% 13% 34%	1710
	11th to 20th	Night	6% 4 1 7% 6% 5% 5% 5% 10% 13% 37%	1710
	21st to end	Night	8% 4 2 5% 6% 6% 7% 6% 9% 14% 33%	1710
July	1st to 10th	Night	7% 6% 3 9% 7% 7% 8% 5% 9% 11% 28%	2840
	11th to 20th	Night	4 5% 3 7% 5% 6% 8% 8% 11% 14% 29%	2840
	21st to end	Night	5% 6% 3 8% 6% 7% 8% 7% 12% 14% 25%	3087
August	1st to 10th	Night	15% 6% 2 7% 6% 6% 7% 5% 8% 12% 26%	2825
	11th to 20th	Night	4 4 2 6% 6% 5% 7% 5% 8% 13% 40%	2785
	21st to end	Night	8% 5% 2 7% 5% 6% 6% 5% 7% 10% 38%	3705
September	1st to 10th	Night	13% 7% 3 9% 6% 6% 5% 5% 8% 10% 29%	2090
	11th to 20th	Night	15% 7% 2 9% 6% 6% 6% 5% 7% 9% 28%	2090
	21st to end	Night	12% 6% 4 8% 5% 4 4 4 7% 8% 37%	2090
October	1st to 10th	Night	14% 6% 2 6% 4 4 4 4 5% 9% 41%	2144
	11th to 20th	Night	7% 4 1 5% 3 4 4 4 5% 7% 56%	2280
	21st to end	Night	8% 4 2 5% 3 4 4 3 5% 7% 53%	2508
November	1st to 10th	Night	10% 5% 2 6% 4 4 4 3 5% 7% 50%	2280
	11th to 20th	Night	11% 7% 2 6% 4 4 5% 4 4 6% 47%	2296
	21st to end	Night	13% 7% 2 5% 4 4 5% 3 6% 8% 44%	2470
December	1st to 10th	Night	11% 6% 3 6% 4 3 4 4 6% 10% 43%	2470
	11th to 20th	Night	14% 6% 2 6% 5% 4 4 3 4 5% 47%	3042
	21st to end	Night	15% 9% 3 7% 5% 5% 5% 3 5% 6% 38%	4532

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	37% 5% 9% 16% 22% 10%	2837
	11th to 20th	Day	40% 4 7% 17% 21% 11%	2840
	21st to end	Day	40% 9% 7% 17% 16% 11%	3124
February	1st to 10th	Day	41% 5% 11% 15% 20% 8%	1852
	11th to 20th	Day	38% 5% 8% 16% 22% 11%	1858
	21st to end	Day	35% 5% 10% 19% 20% 11%	1641
March	1st to 10th	Day	45% 7% 9% 19% 15% 5%	3435
	11th to 20th	Day	26% 8% 17% 18% 16% 15%	3480
	21st to end	Day	39% 6% 10% 20% 17% 8%	3815
April	1st to 10th	Day	30% 6% 13% 23% 18% 10%	2090
	11th to 20th	Day	33% 6% 10% 22% 18% 9%	2157
	21st to end	Day	23% 6% 15% 26% 24% 6%	2332
May	1st to 10th	Day	23% 8% 16% 34% 15% 3	4120
	11th to 20th	Day	37% 9% 15% 23% 14% 2	4085
	21st to end	Day	23% 9% 18% 31% 18% 1	4489
June	1st to 10th	Day	36% 13% 20% 21% 9%	2470
	11th to 20th	Day	32% 14% 20% 27% 8%	2470
	21st to end	Day	38% 16% 23% 17% 6%	2470
July	1st to 10th	Day	38% 17% 26% 17% 2	4055
	11th to 20th	Day	26% 16% 43% 11% 3	4051
	21st to end	Day	31% 21% 33% 13% 2	4324
August	1st to 10th	Day	43% 13% 30% 13% 1	4091
	11th to 20th	Day	27% 14% 26% 24% 10%	4065
	21st to end	Day	38% 13% 22% 25% 2	3930
September	1st to 10th	Day	43% 15% 18% 15% 8% 1	2090
	11th to 20th	Day	48% 11% 16% 16% 8% 1	2090
	21st to end	Day	41% 8% 17% 18% 14% 3	2090
October	1st to 10th	Day	45% 7% 10% 12% 14% 11%	3384
	11th to 20th	Day	18% 6% 8% 21% 33% 13%	3140
	21st to end	Day	21% 5% 8% 23% 34% 10%	3428
November	1st to 10th	Day	33% 7% 12% 19% 19% 10%	1898
	11th to 20th	Day	36% 4 10% 18% 23% 8%	1881
	21st to end	Day	35% 7% 10% 22% 19% 6%	1710
December	1st to 10th	Day	37% 7% 11% 23% 16% 5%	1710
	11th to 20th	Day	39% 6% 11% 17% 21% 6%	2150
	21st to end	Day	44% 6% 8% 18% 18% 6%	3124
January	1st to 10th	Night	40% 5% 8% 13% 22% 13%	4109
	11th to 20th	Night	39% 5% 8% 15% 24% 9%	4120
	21st to end	Night	43% 7% 7% 15% 17% 11%	4532
February	1st to 10th	Night	42% 6% 8% 15% 19% 10%	2323
	11th to 20th	Night	40% 4 9% 16% 19% 12%	2219
	21st to end	Night	38% 5% 10% 19% 15% 11%	1810
March	1st to 10th	Night	48% 7% 12% 14% 13% 7%	3418
	11th to 20th	Night	27% 7% 14% 23% 17% 12%	3480
	21st to end	Night	37% 5% 10% 17% 20% 10%	3817
April	1st to 10th	Night	30% 8% 14% 19% 18% 11%	2090
	11th to 20th	Night	31% 7% 9% 25% 20% 9%	1970
	21st to end	Night	24% 5% 15% 26% 23% 6%	1862
May	1st to 10th	Night	23% 11% 18% 28% 16% 3	2840
	11th to 20th	Night	35% 9% 18% 23% 13% 2	2813
	21st to end	Night	25% 10% 15% 30% 18% 1	3087
June	1st to 10th	Night	37% 11% 20% 21% 10%	1710
	11th to 20th	Night	33% 12% 22% 24% 8%	1710
	21st to end	Night	36% 14% 27% 17% 6% 1	1710
July	1st to 10th	Night	41% 14% 26% 17% 1 1	2795
	11th to 20th	Night	36% 21% 31% 9% 3	2786
	21st to end	Night	41% 17% 26% 14% 2	2988
August	1st to 10th	Night	46% 15% 27% 10% 1	2814
	11th to 20th	Night	30% 14% 24% 24% 8%	2812
	21st to end	Night	37% 12% 21% 27% 2	3705
September	1st to 10th	Night	46% 13% 17% 15% 7% 1	2090
	11th to 20th	Night	48% 13% 17% 14% 8%	2090
	21st to end	Night	42% 9% 14% 17% 15% 3	2090
October	1st to 10th	Night	47% 6% 9% 12% 14% 11%	3573
	11th to 20th	Night	21% 4 7% 19% 31% 18%	3779
	21st to end	Night	20% 5% 8% 19% 34% 13%	4120
November	1st to 10th	Night	35% 6% 9% 18% 20% 11%	2280
	11th to 20th	Night	38% 6% 8% 17% 22% 9%	2296
	21st to end	Night	38% 5% 10% 20% 18% 8%	2470
December	1st to 10th	Night	35% 7% 16% 22% 17% 5%	2470
	11th to 20th	Night	39% 5% 8% 18% 22% 7%	3044
	21st to end	Night	47% 6% 10% 15% 18% 4	4532

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	11% 16% 41% 25% 7%	270
	11th to 20th	Day	4 14% 33% 34% 12% 2	270
	21st to end	Day	16% 17% 41% 23% 3	297
February	1st to 10th	Day	18% 13% 30% 31% 8%	270
	11th to 20th	Day	19% 10% 40% 26% 6%	270
	21st to end	Day	11% 13% 34% 36% 5%	296
March	1st to 10th	Day	11% 13% 33% 31% 12%	460
	11th to 20th	Day	12% 12% 32% 31% 10% 3	460
	21st to end	Day	12% 11% 35% 30% 10% 2	506
April	1st to 10th	Day	10% 14% 32% 29% 14% 2	460
	11th to 20th	Day	11% 10% 28% 31% 16% 4	452
	21st to end	Day	5% 6% 29% 35% 19% 6%	460
May	1st to 10th	Day	5% 7% 23% 38% 22% 6%	463
	11th to 20th	Day	7% 2 21% 36% 27% 7%	487
	21st to end	Day	8% 3 11% 32% 32% 14%	529
June	1st to 10th	Day	13% 2 9% 31% 33% 12%	490
	11th to 20th	Day	7% 2 13% 29% 30% 19%	490
	21st to end	Day	7% 2 7% 29% 36% 19%	490
July	1st to 10th	Day	6% 1 4 22% 41% 25%	485
	11th to 20th	Day	5% 1 2 19% 44% 28%	484
	21st to end	Day	6% 1 6% 22% 47% 18%	532
August	1st to 10th	Day	7% 2 6% 23% 40% 21%	486
	11th to 20th	Day	5% 1 4 21% 41% 27%	479
	21st to end	Day	11% 3 8% 23% 36% 20%	539
September	1st to 10th	Day	14% 2 8% 25% 33% 18%	490
	11th to 20th	Day	13% 5% 11% 32% 30% 10%	490
	21st to end	Day	13% 2 11% 28% 33% 13%	490
October	1st to 10th	Day	15% 5% 20% 35% 20% 6%	490
	11th to 20th	Day	7% 6% 25% 33% 23% 6%	490
	21st to end	Day	12% 5% 18% 40% 23% 4	539
November	1st to 10th	Day	15% 6% 23% 33% 19% 4	472
	11th to 20th	Day	16% 9% 29% 34% 11% 2	441
	21st to end	Day	14% 11% 27% 36% 11%	270
December	1st to 10th	Day	11% 9% 33% 34% 10% 3	270
	11th to 20th	Day	20% 10% 29% 32% 9%	270
	21st to end	Day	13% 11% 29% 34% 11% 1	297
January	1st to 10th	Night	14% 11% 36% 30% 8% 1	760
	11th to 20th	Night	11% 10% 30% 36% 13% 1	760
	21st to end	Night	16% 11% 37% 31% 5%	836
February	1st to 10th	Night	18% 9% 31% 33% 10% 1	760
	11th to 20th	Night	18% 11% 30% 33% 8%	743
	21st to end	Night	15% 8% 31% 39% 6%	628
March	1st to 10th	Night	10% 9% 31% 38% 12%	760
	11th to 20th	Night	13% 8% 28% 37% 13% 1	760
	21st to end	Night	11% 8% 28% 38% 14% 1	836
April	1st to 10th	Night	10% 8% 32% 36% 13% 1	760
	11th to 20th	Night	10% 8% 28% 33% 19% 2	751
	21st to end	Night	6% 4 22% 46% 21% 1	722
May	1st to 10th	Night	7% 4 19% 42% 25% 3	570
	11th to 20th	Night	7% 2 19% 34% 31% 7%	561
	21st to end	Night	10% 3 8% 33% 41% 6%	617
June	1st to 10th	Night	9% 2 8% 37% 37% 7%	570
	11th to 20th	Night	7% 1 8% 32% 39% 14%	570
	21st to end	Night	9% 1 6% 29% 43% 12%	570
July	1st to 10th	Night	8% 1 6% 24% 47% 14%	555
	11th to 20th	Night	5% 1 3 21% 50% 20%	552
	21st to end	Night	5% 1 5% 23% 54% 11%	624
August	1st to 10th	Night	8% 1 6% 21% 50% 13%	567
	11th to 20th	Night	8% 1 4 17% 52% 18%	564
	21st to end	Night	13% 2 7% 22% 41% 16%	820
September	1st to 10th	Night	13% 2 8% 24% 44% 10%	760
	11th to 20th	Night	15% 3 10% 25% 41% 7%	760
	21st to end	Night	15% 4 9% 26% 39% 7%	760
October	1st to 10th	Night	17% 3 18% 29% 28% 5%	760
	11th to 20th	Night	8% 6% 18% 36% 29% 4	760
	21st to end	Night	10% 5% 20% 33% 30% 2	836
November	1st to 10th	Night	13% 5% 22% 36% 22% 2	760
	11th to 20th	Night	14% 8% 27% 31% 18% 2	760
	21st to end	Night	15% 8% 26% 33% 16% 2	760
December	1st to 10th	Night	13% 10% 24% 33% 19% 1	760
	11th to 20th	Night	14% 10% 26% 31% 16% 3	760
	21st to end	Night	17% 10% 25% 33% 15%	836

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